XWT stands for Eclipse XML Window Toolkit. It is a powerful and lightweight declarative UI framework designed for Eclipse, based on XML as markup language.
XWT simplifies UI development by a physical separation of UI definition in XML from the run-time logic in programing language. It is very intuitive for creating interfaces directly or via tools such as Eclipse WindowBuilder. Especially for people with a background in web design and technologies.
More details http://projects.eclipse.org/projects/technology.xwt and http://wiki.eclipse.org/E4/XWT (old) Latest Release Update Site: http://download.eclipse.org/xwt/updates/